The present invention relates to a process and device for intensive heat and material transfer to elongated solid charges or charges on an elongated substrate.
Various suggestions for improving the thermal efficiency of furnaces and for heating up charges in continuous furnaces are known. In this respect it is known to employ recuperative heat exchangers whcih are situated outside the furnace chamber and make use of the heat from the hot gases leaving the furnace to pre-heat the air for combustion and/or the gaseous fuel.
From the French Pat. No. 2 362 353 it is also known to suck the hot gases repeatedly out of the furnace and to blow them into the furnace again via slit-type nozzles. This method can be used only in connection with heating gas temperatures which can be withstood by the impeller and therefore much lower temperatures than the 1000.degree.-1200.degree. of the flames.
From the German patent application DE-OS No. 26 20 211 it is known that the heat transfer from a heating gas to an elongated charge moving in the opposite direction can be improved by blowing jets of colder secondary gas under pressure onto the charge.
The object of the present invention is to develop a process and device for intensive heat or material transfer between a gas and an elongated, solid system such as individual solid bodies in the form of rod, strip, wire or the like, or a plurality of solid bodies positioned in one or more rows on an elongated support. The heat or material transfer takes place in most cases over the whole length of the above mentioned system, preferably in continuous movement; the process of the invention can however also be advantageously employed to heat up one end of an elongated body which is not moving, for example a metal ingot which is to be extruded.
With the described type of heat or material transfer it can for various reasons be advantageous, apart from intense material or heat transfer, to achieve efficient use of the gas viz., as follows:
(a) For the case of heat transfer from the gas to the solid system, maximum utilization of the heat content of the gas. PA1 (b) For the case of heat removal by the gas from the solid system, heating the gas up to the highest possible exit temperature for possible further use of the extracted heat. PA1 (c) For the case of material transfer from the solid system via the gas, reaching a highest possible concentration of the material in the exiting gas in order to facilitate recovery of the said material or for rendering the same harmless. PA1 (d) For the case of material transfer from the gas to the solid system, minimum possible concentration of residual material in the exiting gas.